In this paper, we propose a new research model that describes why users leave social network services. Multiple models and theories were proposed in the past that describe why users join in on innovation, become active users of new IT solutions and adopt technology. But no concise model has been established that explicitly focuses on why users withdraw from social network services – or web based technology in general. The goal of this paper is to develop, based on established theories of information systems research, a research model that provides a predictive set of rules for analyzing user withdrawal from social network services.

A major challenge in adopting UML in industrial environments is the lack of accessibility and comprehensibility of some diagram types by non-technical stakeholders. Literate Modeling improves comprehension of these diagrams by adding narrative text, but lacks good tool support for synchronizing model and text. This paper presents an approach for keeping model and text synchronized by effectively combining state-of-the-art natural language processing technology with OCL model querying. Thereby, consistency of element names in the UML model with their counterparts in the text is achieved by using text annotations to provide the semantic link. At a structural level, we propose an algorithm that checks element relationships in the UML model using a set of validation constraints when particular sentence characteristics are detected. An analysis of the runtime complexity shows the feasibility of including the proposed solution in one of today’s CASE tools.

Our aim is to provide a complete set of materials to teach OCL. They can be used in bachelor or master programs of computer science curricula and for training in an industrial context. In this paper we present the first part of the course related to the OCL Standard Library. This part provides model independent examples to teach OCL types and their operations. It enables users to gain a basic understanding of the OCL Standard Library, which can be used as a starting point to write model constraints (OCL specifications) or model queries. Additionally, to the content of the paper, we provide a set of OCL packages, exercise proposals and lecture slides.

In software engineering practice, measurements may reduce development costs by improving processes and products at early stages. In model driven approaches, measurements can be conducted right from the start of a project. For UML models, a collection of metrics has been empirically validated, however, these need to be precisely defined in order to be useful. Definition of UML metrics in OCL offers a high degree of precision and portability, but due to shortcomings of this language this approach is not widespread. We propose the SQUAM framework, a tool-supported methodology to develop OCL specifications, which incorporates best practices in software development, such as libraries, testing and documentation. As a proof of concept we have developed 26 metrics for UML class diagrams in the academic context. This demonstrated the high effectiveness of our approach: quick learning, high satisfaction of developers, low imposed complexity and potential time reduction through reuse.

Previously we have developed the idea of an Integrated Development Environment for OCL (IDE4OCL). Based on the OCL community's feedback we have also designed and published an IDE4OCL feature model. Here we present a report on selected OCL tools developed by the authors and their teams. Each author gives an overview of their OCL tool, provides a top level architecture, and gives an evaluation of the tool features in a web framework. The framework can also be used by other potential OCL users and tool developers. For users it may serve as an aid to choose a suitable tool for their OCL use scenarios. For tool developers it provides a comparative view for further development of the OCL tools. Our plans are to maintain the collected data and extend this web framework by further OCL tools. Additionally, we would like to encourage sharing of OCL development resources.

With the increasing number of service oriented system implementations, new challenges concerning their development and testing are emerging. This paper presents an approach for model–driven system testing of service oriented systems. The approach offers a systematic testing methodology and it is based on tightly integrated system and test models with a formal metamodel. The test code generation itself is supported by automatic consistency and coverage checks and has a flexible adapter concept that allows different target technologies to be integrated.

This paper reports on the 9th OCL workshop held at the MODELS conference in 2009. The workshop focused on the challeges of using OCL in a variety of new scenarios (e.g., model verification and validation, code generation, test-driven development, transformations) and application domains (e.g., domain-specific languages, web semantics) in which OCL is now being used due to the increasing popularity of model-driven development processes and the important role OCL play in them. The workshop included sessions with paper presentations and a final round discussion.

An Integrated OCL Development Environment (IDE4OCL) can significantly improve the pragmatics and practice of OCL. Therefore we started a comprehensive requirement analysis with the long term vision of a multisite IDE4OCL project. In this paper we present a feature model for the IDE4OCL vision based on this analysis. In an earlier work we identified domain concepts, tool–level interactions with IDE4OCL, and use cases for OCL developers including a set predefined features. In the second step, we asked the OCL community members for their feedback on our proposal. Around 100 researchers, tool developers and practitioners who gained experience with OCL have voted in an online–survey. The results gave us a valuable insight in the needs of OCL usage both in usual and advanced OCL applications. One of the important results is a collection of features that have been proposed additionally to our predefined features. We analysed all the comments of the participants of the survey and consolidated them into an extended set of IDE4OCL features and eventually into a feature model.

The introduction of systematic modelling practices in an enterprise is a demanding task. Mainly, the challenges are related to ensuring a sustaining modelling culture, especially in smaller IT departments. In this paper, we analyse experiences from a modelling project in an industrial setting. The major goal was to improve the documentation quality of the existing, widely informal process model and to establish a commonly accepted modelling culture. During the project, a UML profile was iteratively developed and applied to a model. Furthermore, OCL has been used for automatised quality assessment by model querying. Major benefits, observed by the industry partner, were improved knowledge sharing among the project participants supported by an intuitive modelling notation and automatic information retrieval from the model. Moreover, we describe our adaptations of applied methodologies and quality improvements achieved in the project.

An Integrated OCL Development Environment (IDE4OCL) can significantly improve the pragmatics and praxis of OCL. We present the domain concepts, tool–level interactions with OCL and the use cases we identified in a systematic analysis of requirements for an IDE4OCL. The domain concepts is an important contribution of our work as it attempts to clarify inconsistencies in the relevant specifications. Because OCL is not a stand–alone language, the OCL landscape includes several interacting tools including an IDE4OCL. The use cases describe our vision of the desired functionality unique to an IDE4OCL. The results of our analysis and the long term vision of our work should be relevant to developers of OCL tools as well as to the OMG Request for Information regarding the UML Futures1. Our work is relevant to the UML Futures Roadmap because providing OCL for the constraints in the UML specification has been a longstanding problem at the OMG.

With the increasing number of service oriented system implementations, new challenges concerning their development and testing are emerging.This paper presents an approach for model--driven system testing of service oriented systems. The approach offers a systematic testing methodology and it is based on tightly integrated system and test models with a formal metamodel. The test code generation itself is supported by automatic consistency and coverage checks and has a flexible adapter concept that allows different target technologies to be integrated.

The usage of the Unified Modeling Language in the industrial context becomes increasingly popular. There is an agreement in academia that the Object Constraint Language (OCL) is suitable for defining model constraints and queries. However, it has not yet been broadly adopted by practitioners because they find it difficult to define OCL expressions. Thus, simplification is desirable to increase the use of OCL in practice. We propose OCL libraries (OCLLib), which simplify the development of OCL expressions and enable a high reuse factor, are configurable, testable (OCLUnit) and documented (OCLDoc). In this paper we present the underlying concepts related to OCL library development we used in UML specific and domain specific projects conducted in academic and industrial contexts, respectively.

The size of Unified Modeling Language (UML) models used in practice is very large and ranges up to hundreds and thousands of classes. Querying of these models is used to support their quality assessment by information filtering and aggregating. For both, human cognition and automated analysis, there is a need for fast querying. In this context performance of model queries becomes an important issue. We investigated performance characteristics of two differ- ent querying engines: one using the Object Constraint Lan- guage (OCL) and the other using Prolog. Our comparison is based on equivalent queries in both languages. We ap- plied the queries to 118 models of a size up to 10000 classes to analyze model load and evaluation time. Our preliminary results show that if execution time of queries is linear then Prolog is faster. For one of the presented cases, the execu- tion time in Prolog was nonlinear and thus higher. Further studies should focus on a performance analysis reflecting expressiveness aspects. Our experimental material is ac- cessible to enable future replications of this study.

Moderne Serviceorientierte Systeme werden immer komplexer, was hohe Anforderung an ihre Qualitatssicherung stellt. Die Qualitatssicherung Serviceorientierter Systeme weist allerdings eine Reihe von Spezifika wie die Komplexitat des Aufbaus der Testinfrastruktur auf, die durch die heute verfugbaren Testmethoden und Testframeworks nicht abgedeckt sind. Telling TestStories, kurz TTS, versucht diese Probleme durch die Bereitstellung einer Testmethode und eines Testframeworks fur die modellbasierte Definition, Durchfuhrung und Auswertung von Akzeptanztests auf Basis von Anforderungsspezifikationen zu losen. Im Bereich des modellbasierten Testens von Anforderungsspezifikationen gibt es derzeit erst wenige Ansatze, die sich vor allem auf die automatische Generierung von Testfallen aus Modellen der Anforderungsspezifikation fokussieren wie [BL02, NF06] oder das EU-Projekt Agedis. Unser Ansatz unterscheidet sich von diesen existierenden Ansatzen vor allem darin, dass die Testfalle nicht aus der Anforderungsspezifikiation abgeleitet werden, sondern auf Basis der Elemente der Anforderungsspezifikation von Testern oder Kunden modelliert und ausgefuhrt werden. Dies hat den Vorteil, dass keine vollstandige Anforderungsspezifikation wie sie in der Praxis selten vorliegt benotigt wird, um zuverlassige Testplane entwickeln zu konnen. In den folgenden Abschnitten geben wir einen Uberblick uber die TTS–Methode bzw. das TTS– Framework, beschreiben unsere Implementierung und geben abschliesend einen Ausblick.

In diesem Artikel beschreiben wir einen neuen Ansatz für das anforderungsbasierte Testen Serviceorientierter Systeme. Unser Ansatz beinhaltet sowohl eine Testmethode, welche Teile der Anforderungsspezifikation zur Modellierung von Testabläufen nützt, als auch ein Testframework, mit welchem es möglich ist, aus den Testabläufen konkrete Testfälle zu generieren, diese auszuführen und zu verwalten. Dadurch wird es möglich, Teile der Anforderungsspezifikation ”‘ausführbar”’ zu machen, was deren Qualität und damit auch jene des Systems als ganzes entscheidend verbessert.

Specification and implementation of tests for complex, multi– user systems, like those based on SOA, is a demanding and time–consuming task. To reduce time and effort the specification of tests can be done at the model level. We propose platform independent test specification with our extension of the UML Testing Profile. The three phases of our approach: test design, generation and execution, are explained on an exemplary simple application. We show the differences and similarities of a desktop and a web services variant of the application in context of all phases. At the model level the approach abstracts from platform specific information, nevertheless this information is provided at the test infrastructure level of a proposed architecture. Based on the example application we point out extension possibilities of general character (templates, data pools) and specific for web services (integration with WSDL, BPEL).

In an effort to develop a meaningful and sustainable study programme, the Polish Virtual University (PVU) has undergone a dramatic transition from the formula of a traditional university adapted for the purpose of online learning and teaching to a fully integrated, student-centred modern higher education institution functioning in the environment of e-learning. The independence of students as clients and addressees of the virtual university offer has been nurtured in the course of the PVU’s transition, and the practice of online tutoring has improved significantly. The student and tutor support system has been developed and become a critical component of the PVU system. This article gives an overview of the actions initiated at the PVU which helped to create an atmosphere of fearless learning and support students in their pursuit of knowledge expansion and upgrading practical skills. It also discusses the importance of taking into consideration the whole scope of overlapping commitments that online students have to cope with.

This paper presents an enterprise-modelling oriented approach to IT Governance. Main requirements for a IT Governance Framework are presented and applicability is shown by means of operationalizing Strategic Alignment -- a main focus area of IT Governance. Two frameworks are briefly described, namely PRO2SA (domain-specific for Strategic Business Alignment) and the general-purpose framework SQUAM for metamodelling, enterprise modelling and model-analysis. Key aspects of this approach are the information enrichment of enterprise models (mainly with key figures) and the integration into a Business Intelligence Suite for comprehensive business analysis.